Download 4. Flexural Members PDF

Title4. Flexural Members
TagsBending Beam (Structure) Stress (Mechanics) Materials Science Structural Engineering
File Size942.9 KB
Total Pages20
Document Text Contents
Page 1

Mapua Institute of Technology
School of CE-EnSE-CEM

STEEL & TIMBER DESIGN

Lecture Notes of Engr. Edgardo S. Cruz, MSCE [email protected]

FLEXURAL MEMBERS

Design of Flexural Members

Classification of Steel Section:
1. Compact Section
2. Non – Compact Section
3 Slender Element Section3. Slender Element Section

Stiffened Element – supported along two edges parallel to the direction of the
compression force.
Unstiffened Element – supported along one edge, parallel to the direction of the
compression force.

Compact SectionCo pact Sect o
bf < 170 (for compression flanges of I – Section and Channel Section)

2tf √Fy

d < 1680
tw √Fy (for webs in flexural compression)

Page 2

Mapua Institute of Technology
School of CE-EnSE-CEM

STEEL & TIMBER DESIGN

Lecture Notes of Engr. Edgardo S. Cruz, MSCE [email protected]

Non – Compact Section
bf < 250 (for compression flanges of I – Section and Channel Section)
2tf √Fy

h < 1995
tw √Fy (for webs in flexural compression)

Slender Element Section
bf > 250 (for compression flanges of I – Section and Channel Section)
2tf √Fy

h > 1995
tw √Fy (for webs in flexural compression)

*NOTE:
Compact Sections - ALL of its elements must be compact.

For sections other than mentioned above, please see
Table 5-1-Limiting Width Thickness Ratio for Compression
Members (page 194 of Gillesania).

Allowable Bending Stress for I – Section & Channel Section
Bent About Their Major Axis

1. Members with Compact Section with Lb < Lc ; Lb=braced length

(allowable bending stress in both tension & compression)

2. Members w/ Non – Compact Section

a. For except that their flanges are non – compact (excluding
built – up members & members w/ ).built up members & members w/ )

Page 10

Mapua Institute of Technology
School of CE-EnSE-CEM

STEEL & TIMBER DESIGN

Lecture Notes of Engr. Edgardo S. Cruz, MSCE [email protected]

single curvature
4.

5.

single curvature

•Members with Compact Sections

Allowable Bending Stress, of I – Section, Solid Bars, Channel &
Plates on Their Weaker Axis.

•Members with Non – Compact Sections

Shear Stress on Beams,

Page 11

Mapua Institute of Technology
School of CE-EnSE-CEM

STEEL & TIMBER DESIGN

Lecture Notes of Engr. Edgardo S. Cruz, MSCE [email protected]

Allowable Shear Stress,

*When or

*When or

where:

when when

when when

where:

Sample Problem 3:

From sample problem 1, check the adequacy of the beam against shear.

a.

b.

c.

d.

Page 19

Mapua Institute of Technology
School of CE-EnSE-CEM

STEEL & TIMBER DESIGN

Lecture Notes of Engr. Edgardo S. Cruz, MSCE [email protected]

B. WEB CRIPPLING

SAMPLE PROBLEM 5

A simply supported beam carries a concentrated load at the center of the wide
flange section having a web thickness of 14.7mm. The base plate placed
directly on the load is used to prevent web yielding & crippling has a width “N”
of 600mm, k= 31mm, Fy= 250 Mpa
a Determine the max concentrated load that the base plate can carrya. Determine the max concentrated load that the base plate can carry.
b. Determine the minimum length (N) of bearing plate to be placed under
supports.

P

6m

Page 20

Mapua Institute of Technology
School of CE-EnSE-CEM

STEEL & TIMBER DESIGN

Lecture Notes of Engr. Edgardo S. Cruz, MSCE [email protected]

tw = 14.7mm
N= 600mm
k = 31mm
Fy=250Mpa
d=550mm
tf = 23.6mm

P

6m

Solution:

R= P/2 R= P/2

a. Pmax @ midspan=?
Web Yielding, x = 3 d = 0.55m

x > d ; Case b

;

P = 1831.2525 KN ans.

Web Crippling x = 3 d = 0 55mWeb Crippling, x = 3 d = 0.55m
x > d/2 ; Case a

P = 2001.32 KN

Pmax = 1831.2525 KN ans.

a. Nmin @ supports=?

Web Yielding, x = 0 d = 0.55m
x < d ; Case a

; ;

Web Crippling, x = 0 d = 0.55m
x < d/2 ; Case b

Nsup = 300 mm

Nsup = 510.34 mm

.: Nmin @ support = 510.34mm ans.

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